1. Field of the Invention
This invention relates to an apparatus for the inspection of printed circuits on which components have been mounted. More particularly, it relates to an apparatus that inspects for a dislocation of components mounted on a printed circuit board, an unsatisfactory soldering of the components, solder bridges of the components, or the like by the use of narrow beam spots.
2. Description of the Prior Art
Conventional methods for automatically inspecting for a dislocation of components mounted on printed circuit boards, an unsatisfactory soldering of the components and solder bridges of the components, or the like include a method that uses light beams from light emitting devices through multi-slit and a camera. FIG. 1 shows a model of the inspection apparatus for finding inspection of the dislocation of components mounted on a printed circuit board, or the like by this method. Two light beams from multi-slit-type light radiating devices 55 and 56 obliquely are radiated onto a printed circuit board 57 on which components have been mounted so that their optical axes intersect at right angles. Through observation with a camera 54 located above, the height of each of the mounted components can be measured based on the principles of triangulation. The position of each component in the directions of x and y (refer to FIG. 4) can also be determined by radiating beams from the multi-slit-type light radiating devices 55 and 56.
However, the constitution as described above is disadvantageous for the following reasons. In an inspection of solder surfaces of the components, because the reflection and scattering characteristics of the solder surface are similar to those of a mirror, light reflected from the solder surfaces becomes excessively strong or weak depending on a relationship between the inclination of the solder surface and the position of the camera, so that the camera cannot function as a sensor. Moreover, cameras have limitations to their fields of view, and it happens that only a part of the components to be inspected can be covered by the field of view of the cameras. In this case, image information from multiple fields of view is required to inspect a single component, which makes the inspection software thereof complicated.